This invention relates to a toner application method for developing electrostatic latent images with a toner and a composition therefor.
Conventionally, various types of apparatus have been proposed and put into practice as a dry type one-component developer apparatus. However, in any of those types, it has been very difficult to form a thin layer of one-component dry developer, so that a relatively thick layer of the developer is used. On the other hand, the recent desire for the improved sharpness, resolution or other qualities of developed images has necessitated the achievement of a system for forming a thin layer of one-component dry developer.
A method of forming a thin layer of one-component dry developer has been proposed in Japanese Laid-Open patent application No. 43037/1979 and has been put into practical use. However, this method is directed to the formation of a thin layer of a magnetic developer, not of a non-magnetic developer. The particles of a magnetic developer must each contain a magnetic material in a large proportion to gain a magnetic property. This is disadvantageous since it results in poor image fixing characteristic when the developed image is heat-fixed on a recording paper to be transfer-printed. Further, because the magnetic material is generally black or dark-brown in color, it is difficult to obtain a clear color image by using a megnetic toner.
For this reason, there have been proposed methods for forming a thin layer of non-magnetic developer such as a method wherein a developer is applied by attaching it to a cylindrical brush made of soft hair such as that of a beaver, and a method wherein a developer is applied onto a developing roller, the surface of which is made of fiber such as velvet by means of an application means such as a doctor blade. However, when a fiber brush is used in combination with an elastic blade, it is possible to control the amount of the developer, but uniform application is not effected. Moreover, only the fiber brush on the developing roller is rubbed and triboelectric charge is not imparted to the developer present between fibers of the brush, whereby a defect such as ghost is liable to occur. Further, because a non-magnetic developer is used, it is difficult to prevent the leakage of the developer out of the apparatus.